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A2 OCR Chemistry Practical Exam (26/5/05)

Hi

Just thought I'd start a message on this exam. What are people expecting from it?

anyone? I was thinking a titration and maybe something else like heating something or some test tube reactions or something.

bump

I don't reckon it can be a titration AND something else.. Cos the titrations take long enough as it is! But i do reckon it'll be some sort of titration... It always is!

the AS wasn't...

The main thing we have practiced this year is titrations so I hope it is one of these.

Reply 6

violet

El Stevo

the AS wasn't...

Yeh but the A2 planning is a titration.. Kind of gives it away.. I still reckon it is and that's one of the only kinda of expts we've done this year so all i'm gonna practice is the calculations and hope all goes well on the day! :redface:

Reply 7

alwaysingtogeth

Another tip I'd give is to practice or look at mark schemes from previous evaluations. They all seem to be fairly similar and it is 14 marks out of 60 (44 on the day). They always seem to get you to say why the method you did was good/bad and often show another experiment that you have to criticise. not repeated/not accurate enough equipment etc.

Reply 8

t_muir11

We've been told to expect a back-titration, similar to the planning exercise. Also, quite possibly an iodine titration and using starch as the indicator. To be honest though, I'm a little worried about how much other chemistry I'll need to bring in - if they do some other little experiments as well, will colour changes etc be required. If anyone knows how to get hold of some past paper mark schemes for the prac I'd be grateful.

Reply 9

fluorescentpink

in class in the last month or so, weve done titrations wit iodine using starch as the indicator. and weve also had other little test tube tests to do- prob from the transition metals bit, involving colour changes. we havent done anything other than titrations for a long time.... we would have done if it wasnt a titration... im sure of it.

Reply 10

S-e-r-e-n-d-i-p-i-t-y

hmm.....back titration eh. We did past paper invoving starch indicator and sodium thiosulphate....but i dunno, it could be the reaction involving the iron ions, but this is unlikely as it was in the plan
:eek:

Reply 11

unrulyewe

It is more then likely to be a titration as the plan gives a very good idea of wot to expect! My class has been doin test tube reactions to show the action of silver nitrate (AgNO3) and wot colour precipitate it produces when added to iodide, bromide and chloride ions, this cud come up also. I think sodium thiosulphate with iodide titration is going to be the one!!

Reply 12

steffi4eva

Does anyone have any ideas where to get past ocr chem prac papers? im stressin quite a bit about it so wud just like to look at the types of questions they might ask us!! thanks!! :smile:

Reply 13

tdubz

could someone tell me the theory behind the thiosulphate and iodide titration because i have a strange feelin this maybe the one, how does it work and why is it different to any other titration?

thanks a lot x

Reply 14

bulldog1234

what questions could they set on this, will they do halide ion displacement reactions

Reply 15

fluorescentpink

i dont know what a halide ion displacement reaction is :s-smilie:

Reply 16

bulldog1234

cl2 + 2br- = 2cl-2 + br2 orange brown liquid is formed

Reply 17

zaaks786

apart frm the titrations we r supposed to be getting litle test tube reactions....possible halide stufff...theres heaps of stuff tht cud be

anyone been given hints?